1. Field of the Invention
The present general inventive concept relates to an image forming apparatus, and more particularly, to an image forming apparatus which is capable of transmitting image data into an imaging drum with high reliability.
2. Description of the Related Art
An image forming apparatus is an electronic device which forms an image on a printing medium with a developing agent. The image forming apparatus is classified into an electrophotographic type which includes processes of electrification, exposure, development, transfer and fixation, and an ink-jet type which jets ink according to a printing method.
A general electrophotographic image forming apparatus includes a charger which uniformly charges a surface of a photosensitive drum to a potential and an exposure unit which exposes the charged surface of the photosensitive drum. However, since the image forming apparatus includes the charger and the exposure unit, spatial efficiency is not improved. Also, since processes of development and transfer are performed by a potential difference, development and transfer efficiencies decrease.
U.S. Pat. No. 4,704,621 discloses an image forming apparatus which uses an imaging drum where a plurality of electrodes are separately disposed on an insulating base instead of a photosensitive drum.
FIG. 1 is a schematic sectional view of a conventional image forming apparatus 1 which adopts an imaging drum 20. The image forming apparatus 1 includes a toner storage part 3 which stores a conductive and magnetic toner T, a cassette 4 which is loaded with a printing paper, a pickup part 6 which picks up the printing paper and a pair of feeding parts 7 which carry the printing paper. G indicates a paper guide, 31 indicates a paper preheating belt, and 33 and 35 indicate paper preheating belt driving parts, wherein the paper preheating belt driving part 33 includes a heating unit therein to heat the paper preheating belt. Reference numerals 43, 45 and 47 indicate a transfer part, a fixing part and a discharging part, respectively.
Meanwhile, the toner storage part 3 accommodates a developing part 10, and a toner in the toner storage part 3 is applied to an outer surface of the developing part 10. Referring to FIGS. 1 and 2, the developing part 10 includes a cylinder-shaped sleeve 15 of a conductive material, a plurality of magnets 11 provided inside the sleeve 15, and a magnetic knife 13 installed in a narrow space between the magnets 11 to generate an intensive magnetic field. Accordingly, the toner in the toner storage part 3 is led by the magnetic field by the magnets 11 in the developing part 10 to be applied to the outer circumference surface of the developing part 10.
Meanwhile, the imaging drum 20, as shown in FIG. 2, is disposed parallel with the developing part 10 with respect to a rotation axis thereof. In the imaging drum 20, a plurality of electrodes 23 are separately disposed on a base 21 of an insulating material, and a dielectric layer 22 encompasses the electrodes 23.
Image data to be printed is converted into an image signal to drive the electrodes 23 of the imaging drum 20 by an image processor 5. A slip ring is provided on a drum shaft 24 of the imaging drum 20 so that the image signal is simultaneously transmitted to an electrode driver (not shown) inside the imaging drum 20 during rotation of the imaging drum 20.
The slip ring is provided as a ring-shaped electrode pad on the outer circumference surface of the drum shaft 24 and rotated in contact with a cylinder-shaped stationary brush (not shown), thereby transmitting the image signal to the electrode driver (not shown). The electrode driver applies a voltage corresponding to the image data to the electrodes 23 connected thereto through lead lines 23a according to the image signal. Accordingly, an induced electric charge is generated in the toner T on the developing part 10 and transferred to the imaging drum 20 by electric magnetism. Thus, a toner visible image corresponding to the image data is formed on the imaging drum 20.
However, when the imaging drum 20 is rotated at a high speed, a contact area between the slip ring 23 and the stationary brush (not shown) is worn out or heat is generated in the contact area. Thus, a transmitted image signal may be distorted. In particular, a printing speed may not increase due to signal distortion.
A slip ring with excellent a wear-out resisting property and thermal stability may be used to prevent the signal distortion, but it increases the cost.